This application is a 371 of PCT/DK95/00320 filed Aug. 3, 1995.
The present invention relates to an apparatus and a method for manufacturing clinker whereby the majority of the raw materials is introduced in a hydrous slurry. The apparatus comprises a gas suspension drier in which the slurry of raw materials is dried and a kiln in which the materials are burned and nodulized.
In connection with the traditional method for manufacturing cement clinker according to a wet process, the raw materials are ground subject to simultaneous addition of water and passed on to the kiln in a slurry so that the drying of the slurry is effected in the first and coldest part of the kiln.
Another possibility involves removal of the water from the raw materials prior to their entry into the kiln. Such a method is described in U.S. Pat. No. 5,173,044 according to which the raw materials are fed to a Gas Suspension Drier (GSD) prior to their entry into the kiln. In this context, the GSD unit is also operating as a scrubber, and, consequently, nearly all of the S0.sub.2 being generated in the kiln is expelled from the exhaust gasses. In this apparatus it is also possible to mix dry and hydrous raw materials in the GSD unit without causing the overall raw material mixture to become inhomogeneous.
However, it has emerged that the temperature profiles experienced during this process will increase the risk of volatile organic compounds being distilled off the raw materials in the first part of the kiln so that they are carried along by the exhaust gases through the GSD unit without being absorbed or destroyed since the temperature in the GSD unit is relatively low.